| Popis: |
Publisher Summary Francisella tularensis is gram-negative, non-motile without capsules or spores. Grown on agar media, it tends to be pleomorphic; coccoid, ovoid, bacillary, bean-shaped, dumb-bell 0.2–0.7 μm in length, where even filamentous forms may be seen. F. tularensis is aerobic and does not grow on ordinary media without enrichment. It grows well on glucose–cystine–blood agar, less well on glucose–cystine agar and coagulated hen's egg yolk medium. Growth occurs also on glucose–blood agar, glucose–serum agar, and blood agar slants provided that a piece of rabbit's spleen is rubbed over the surface. Glucose–cystine–blood agar inoculated with infective tissue may show discrete growth within 2–7 days, but subcultures show confluent growth within 24–48 hours. The colonies are viscous grey and may attain 4 mm in diameter. Glucose, glycerol, maltose, mannose, fructose, and dextrin may be fermented with production of acid, but no gas. F. tularensis is very susceptible to antimicrobial agents, including chloramphenicol and the tetracyclines and is killed by moist heat at 55–60°C within 10 min. F. tularensis appears antigenically homogenous. It shows a weak serological cross-reaction by agglutination with organisms of the genus Brucella and by immunofluorescence with Pseudomonas aeruginosa . |
